University of Oulu

Kalakoski, N., Verronen, P. T., Seppälä, A., Szeląg, M. E., Kero, A., and Marsh, D. R.: Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations: the importance of lower ionospheric chemistry, Atmos. Chem. Phys., 20, 8923–8938,, 2020.

Statistical response of middle atmosphere composition to solar proton events in WACCM-D simulations : the importance of lower ionospheric chemistry

Saved in:
Author: Kalakoski, Niilo1; Verronen, Pekka T.1,2; Seppälä, Annika3;
Organizations: 1Space and Earth Observation Centre, Finnish Meteorological Institute, Helsinki, Finland
2Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
3Department of Physics, University of Otago, Dunedin, New Zealand
4Atmospheric Chemistry Observations and Modeling, National Center for Atmospheric Research, Boulder, CO, USA
5Priestley International Centre for Climate, University of Leeds, Leeds, UK
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.7 MB)
Persistent link:
Language: English
Published: Copernicus Publications, 2020
Publish Date: 2020-10-14


Atmospheric effects of solar proton events (SPEs) have been studied for decades, because their drastic impact can be used to test our understanding of upper stratospheric and mesospheric chemistry in the polar cap regions. For example, odd hydrogen and odd nitrogen are produced during SPEs, which leads to depletion of ozone in catalytic reactions, such that the effects are easily observed from satellites during the strongest events. Until recently, the complexity of the ion chemistry in the lower ionosphere (i.e., in the D region) has restricted global models to simplified parameterizations of chemical impacts induced by energetic particle precipitation (EPP). Because of this restriction, global models have been unable to correctly reproduce some important effects, such as the increase in mesospheric HNO₃ or the changes in chlorine species. Here we use simulations from the WACCM-D model, a variant of the Whole Atmosphere Community Climate Model, to study the statistical response of the atmosphere to the 66 strongest SPEs which occurred in the years 1989–2012. Our model includes a set of D-region ion chemistry, designed for a detailed representation of the atmospheric effects of SPEs and EPP in general. We use superposed epoch analysis to study changes in O₃, HOₓ (OH + HO₂), Clₓ (Cl + ClO), HNO₃, NOₓ (NO + NO₂) and H₂O. Compared to the standard WACCM which uses an ion chemistry parameterization, WACCM-D produces a larger response in O₃ and NOₓ and a weaker response in HOₓ and introduces changes in HNO₃ and Clₓ. These differences between WACCM and WACCM-D highlight the importance of including ion chemistry reactions in models used to study EPP.

see all

Series: Atmospheric chemistry and physics
ISSN: 1680-7316
ISSN-E: 1680-7324
ISSN-L: 1680-7316
Volume: 20
Issue: 14
Pages: 8923 - 8938
DOI: 10.5194/acp-20-8923-2020
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: DRM has been supported by NSF (Award no. 1650918, “Collaborative Research: CEDAR – Quantifying the Impact of Radiation Belt Electron Precipitation on Atmospheric Reactive Nitrogen Oxides (NOx) and Ozone (O3)”). Antti Kero is funded by the Tenure Track Project in Radio Science at Sodankylä Geophysical Observatory.
Copyright information: © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.